1. Technical Field
The present invention relates to a hub reduction gear for a driving wheel of heavy wheeled vehicles, such as military combat vehicles, which gear comprises a planetary gear unit having a sun gear connectable to a drive shaft, a carrier for planet gears, which are in mesh with the sun gear, and a ring gear surrounding the planet gears, said ring gear being in mesh with the planet gears.
2. Background Art
In order to facilitate a very narrow turn, a so called centre or pivot turn, of multiple shaft, wheel supported motor vehicles with drive on several shafts, i.e. bring the vehicle to turn on spot about its mainly vertical centre axis, it has earlier been suggested to use separate drivelines for the left and right driving wheel of the vehicle, such that the left and right driving wheels may be brought to rotate in mutually opposite rotational directions during turn. This system is constructively circumstantial, heavy and expensive and requires a large space in the vehicle.
Another known suggestion for providing mutually opposite rotational directions of the left and right drive shafts of multi shaft, wheel supported motor vehicles and thereby with a centre turn of the vehicle utilizes for each shaft pair a separate controllable, rotational reversing gear between a respective differential and drive shaft on the side of the vehicle. This makes the construction relatively space requiring in the transversal direction of the vehicle.
WO 2007/091963 describes a differential gear being constructed to, apart from the two conventional drive modes “open differential”, i.e. that the output drive shafts from the differential rotate in the same direction with the possibility to rotate with the same rotational speed, and “locked differential”, i.e. when the drive shafts rotate forcibly with the same rotational speed and in the same direction, also be able to provide the additional drive mode “rotation of drive shafts in opposite directions”. This differential gear facilitates to also provide mutually opposite rotational directions of the drive shafts on the left and right side of the vehicle without any separate directional reversing extra gear and thereby a centre turn of the same.
It is further known to build in a hub reduction gear in respective driving wheel of wheel supported, multi shaft motor vehicle in order to provide a desired gear reduction of the rotational speed of the drive shaft to the driving wheels. Such hub reduction gears normally comprises a planetary gear unit having a sun gear connectable to each drive shaft, a carrier for planet gears, which meshes with the sun gear, and a ring gear surrounding the planet gears which meshes with the planet gears. Normally the carrier of the planet gears is permanently fixedly engaged to a part connectable to the wheel rim, while the ring gear is firmly fixed relative to the vehicle body.